help / Jan 07 2019
by David Schmudde

Understanding /results

Output Graphs and Uploaded Images/Data

Fritz Overbeck "Birken in Worpswede" (1908)

1.
Generated Data

Graphical output is stored as a file in the /results directory.

ls
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Plotting mandelbrot.

from numpy import *
from matplotlib import pyplot as plt

def mandelbrot( h,w, maxit=40):
        y,x = ogrid[ -1.4:1.4:h*1j, -2:0.8:w*1j ]
        c = x+y*1j
        z = c
        divtime = maxit + zeros(z.shape, dtype=int)

        for i in range(maxit):
                z  = z**2 + c
                diverge = z*conj(z) > 2**2            
                div_now = diverge & (divtime==maxit)  
                divtime[div_now] = i + 100             
                z[diverge] = 2                        

        return divtime
      
fig = plt.subplots(1,figsize=(20,20))
plt.imshow(mandelbrot(1000,1000)) 
plt.axis('off')
plt.savefig("/results/mandelbrot.png")
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To get data out of Nextjournal, files can be written or copied to the /results directory. Image files will be displayed in the article (right-click to download), while all other files will appear with a download link.

with open("/results/test.txt", "w") as f:
  f.write("Some text.\nSome \"other\" text.")
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test.txt

We can also access files that were previously placed in /results, from other cells or even the same cell if recursion is needed.

with open(test.txt↩) as f:
  print(f.read())
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These are stored in the same database as uploaded files, but to reference these we start by typing the name of the cell that created the file, then again find the file in the autocomplete list.

2.
Uploaded Data

ls Image↩
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cp Image↩ /results/overbeck.jpg
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ls /results
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Files downloaded from within cells can be preserved in either of two ways. The preferred method is to download the file directly into /results, thus ensuring the file will be saved and versioned for reference elsewhere in the article.

import urllib

urllib.request.urlretrieve("https://nextjournal.com/images/logo.svg",
                           "/results/logo.svg")
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They can even be referenced in other runtimes and languages.

cp Image↩ /logo.svg
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3.
Content Addressed Store

mkdir -p results/temp-dir
cp Image↩ results/temp-dir
ls results/temp-dir
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ls -alF results/temp-dir
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Why is there no file in /results/temp-dir?

Every file you write to /results will be moved to our permanent and content addressed storage after the execution of the cell. It is then available as cell result and it can be used as reference in any other cell by using copy/paste. Behind the scenes it is actually moved to a `/data/<content-hash>` file and permanently stored on a google cloud storage nas device. If you paste the reference in any other cell and access it, it automatically resolves to that file.